Filters are used to purify a variety of fluids, including gas and liquid. The filter media used for the purification, over time, will load with contaminant. Filters are used until they are plugged (contaminant blocks all flow through the media) or until a predetermined restriction level is reached. Both are associated with flow and the work necessary to move the flow. Either too little fluid is allowed to flow through, or too much work is required to move the desired flow due to the higher restriction.
In some systems, pulse jet cleaning is used to periodically remove contaminant from the upstream side of the filter media. Using pulse-cleaning increases the life of the filter by decreasing the restriction and increasing the service interval. Pulse-cleaning has been used with pleated filters in arrangements described in U.S. Pat. Nos. 4,364,751; 4,218,227; 4,331,459; and 5,575,826, each of which is incorporated by reference herein.